The safe and efficient control of power plants requires that the plant operator(s) comprehend significant quantities of interdependent data items; more specifically, plant operators must be able to respond rapidly to a wide variety of possible changes in plant operating conditions by taking appropriate control actions. The present invention relates to improved displays for providing plant operators with more readily comprehensible information. The invention is applicable to monitoring and control of all types of nuclear power plants, including those comprising light water reactors, gas cooled reactors, and liquid metal cooled reactors, as well as fossil-fueled power plants. In order to allow complete explanation of the invention, a power plant comprising a pressurized water nuclear reactor is first discussed; use of the invention for monitoring and control of such a plant is then discussed in detail.
As is generally conventional, the power plant comprising a pressurized water reactor described herein consists of four closed reactor coolant loops ("primary coolant loops") connected in parallel to the reactor vessel to form the primary coolant system. A separate power conversion system ("secondary coolant system") converts heat energy received from the primary coolant system to electrical energy. Each primary coolant loop contains a reactor coolant pump, a steam generator, loop piping, instrumentation, and water serving as the reactor coolant. The instrumentation monitors process and system variables. One of the primary coolant loops contains an electrically heated pressurizer for the control of pressure within the primary coolant system.
Liquid phase water is pumped through the reactor core to remove heat generated by nuclear fission. The heated water flows via the primary coolant loop piping to the corresponding steam generator, where heat is transferred to the secondary water, cooling the primary water. The reactor coolant pump then pumps the cooled primary water into the reactor vessel, completing the primary cycle.
Liquid phase water in the secondary system is boiled to steam in the steam generators, as heat is transferred from the hot primary coolant water. Saturated steam exiting from the steam generators is directed to the high pressure steam turbine to perform work on the turbine. After exiting the high pressure turbine, the low energy, moisture laden steam is routed to a moisture separator/reheater where excess moisture is removed and the steam reheated. The reheated steam then enters the low pressure turbine, where it performs further work in driving the turbine. After exiting the low pressure turbine, the low energy moisture laden steam enters the condenser, where it is condensed to liquid phase water via heat transfer to a heat sink. The heat sink is the environment and usually consists of condenser cooling water from a lake, river, or ocean. In some cases, the heat sink may comprise a cooling tower.
The condensed secondary water then enters a hotwell; it is pumped from the hotwell to four parallel strings of feedwater systems, each string containing a hotwell pump, a booster pump, a feedwater pump, and feedwater heaters. Each of the four feedwater systems supplies a steam generator with heated feedwater to complete the secondary cycle. Instrumentation in the secondary system monitors process and system variables.
The overall plant is referred to as including four heat engines, and the overall process of power generation as the heat engine cycle, while the cycle undergone by the water in each secondary system is known as the Rankine cycle. For the pressurized water reactor power plant discussed, having four separate secondary water loops, four Rankine cycles are thus implemented in the overall secondary system, sharing a common turbine and condenser. The thermodynamic process in each cycle consists of heat transfer, heat transport, and work functions. Each of these functions are further described by one or more process variables, such as coolant temperature, pressure, and flow rate. The processes within the associated primary coolant loops also consist of heat transfer, heat transport, and work functions; these functions are also described by process variables such as coolant temperature, pressure, and flow rate. The heat source for the primary coolant is the reactor, and the heat sink for the entire plant is the environment. In summary, then, the heat engine cycles for the plant include four primary coolant loops and the processes therein, and the four associated secondary coolant loops and the processes therein, with the reactor as the heat source and the environment as the heat sink.
The integrity of the physical systems, consisting of the primary coolant system, the secondary coolant system, and the associated process controls, should be maintained and monitored to sustain efficient and safe operation of the plant. The failure of a critical system will impact the process and will initiate the operation of a safety system. Human operators are required to monitor instrumentation for system and process variables in order to determine the status of the plant.
Monitoring the power plant to ensure efficient and safe operation requires the operators to monitor and comprehend a large number of process and system variables and to evaluate a number of process and system functions. The process and system variables may consist of water flow rate, temperature, pressure, pump speed, and the positions of valves at a significant number of points in the power plant. A process function may consist of a heat transfer function, such as the heat transfer from the primary coolant in the steam generator to the secondary coolant in the steam generator. A system function may consist of a process control system regulating the flow of feedwater.
The integrity of the heat engine cycle must be monitored to ensure that the reactor is continually cooled and operated in a safe and efficient manner. For example, the detection of a hot bearing in a coolant pump will require operator action to compensate for the loss of the pump. The loss of a coolant pump will disturb the flow of heat energy through the heat engine cycle, possibly resulting in the approach of unsafe operating conditions, such as undue heating of the reactor.
The process parameters and functions that must be monitored for proper operation of a typical pressurized-water reactor nuclear power plant include the power generated by the reactor, the heating of the coolant water by the reactor, the heat transfer from the primary coolant water to the secondary water in the steam generator to produce steam, the work done by the steam in driving the high pressure turbine, reheat of the high pressure turbine exhaust steam before supply to the low pressure turbine, work performed by the steam in driving the low pressure turbine, condensation of the low pressure turbine exhaust steam in the condenser, and the recirculation of the condensed water to the steam generators through their respective feedwater systems.
Those of skill in the art recognize that this brief list represents a substantial simplification of the overall process variables, system variables, and functions to be monitored. Nonetheless, it will be apparent that effectively monitoring even this limited number of variables and functions over a typical shift is a difficult task, particularly when disturbances occur in the plant. Further, noting that typical plants contain as many as four sets of feedwater heaters and steam generators, it will be apparent that simplifying the operator's cognitive tasks and monitoring duties and rendering their performance as intuitive as possible would be highly desirable.
Monitoring of fossil-fueled power plants involves comprehension of a similar number of critical process and system variables, as well as numerous critical functions.
The most pertinent prior art disclosure known to the inventor as of the filing of this application is his United States Statutory Invention Registration H289 entitled Integrated Iconic Display. According to this disclosure, the principal process variables describing the thermodynamic process for one heat engine cycle, that is, the variables describing one primary coolant loop and the corresponding single secondary cooling loop, were shown by illustrating the temperature profile in the respective loops on a CRT display employing temperature and entropy as the coordinates of the display. Although this disclosure represented a useful and informative display, presentation of the thermodynamic process in this form required a great deal of display space. In particular, a display screen was needed for each heat engine cycle in the plant, and therefore separate screens were required to show process conditions in each heat engine comprised by the plant. Monitoring of a typical plant including up to four such heat engines by one person was very difficult, as the data to be monitored was not all displayed in one field of view. This made it difficult, for example, to compare the performance of the several heat engine cycles to one another and to detect differences in performance when they existed.
Alternative display arrangements for power plant monitoring shown in the prior art include a piping diagram of the coolant loops displayed on a screen with values for sensed process data displayed therein; such displays tended to intermix process data, such as temperature and pressure, with system data, such as pump and valve status. The intermixing of process data and system data made it difficult for the user to gauge the process data separately from the system data; that is, the operators found it difficult to monitor the total performance of each heat engine cycle and to reason in real time on the operation of the plant during plant disturbances. More specifically, the lack of integrated process data for the entire plant made it difficult for operators to reason using the thermodynamic first principles upon which the plant was designed.
Also, prior art display arrangements have not used the same temperature grid to display all of the heat engine cycles of a given plant, nor provided convenient displays of the temperature trends for sensed temperatures and computed temperatures within the heat engine cycle.